How can tuna/bonito be tested for histamine?

Question

I think I suffered scombroid food poisoning, together with some other people. I actually got the worst of it. The others experienced pain in the mouth. I had facial flushing and tachycardia as well.

This is not the first time this happens as we've experienced pain from both tuna and bonito. Both cooked and raw (tartar).

According to the Wikipedia, this can be due to inappropriate handling of the fish. I bought this last bonito from a fish shop five minutes walking away. I guess it's hardly likely that the error was on me, but I won't rule it out neither. My handling of the bonito was to cut it up, put it into a vacuum bag and freeze. The batch that made us ill was vacuum and unfrozen. I've got more tuna from the same batch in the freezer, so I'll have to throw that out. That's one shop where I'm not buying anymore.

Is there a way of testing for histamine to prevent future problems?

Answer

If you say that your handling of the fish was a 5 minute walk and to cut it up and freeze it, it is more than likely that the contamination occurred during the supply chain. Once the enzyme histidine decarboxylase has been formed, it can continue to produce histamine in the fish even if the bacteria are not active.

There are test kits available for checking histamine levels but they are intended for commercial use. http://www.noackgroup.com/Live/ProductCatalog_en.YoCms?GROUP=%24D_FAA_07_01#_1NEO9505 is one of the places that has them.

Check more discussion of this question.

Should tuna steaks sit out before cooking?

Question

If beef steak needs to sit outside the refrigerator before cooking, should the same thing be done for tuna steaks too?

Answer

The same logic applies. The smaller the temperature difference between uncooked and cooked, the easier it will be to get an even amount of cooking all the way through. Especially with a fast method of cooking like broiling.

Check more discussion of this question.

Why would fresh tuna be salted?

Question

I bought a big piece of tuna about a week ago. I carved it up and put most in the freezer. However, as I am the proud owner of a vacuum sealer (as of a week ago), the worst part of the tuna got vacuum sealed and put into the fridge.

Six days later, I took it out of the fridge to cook, and found that the vacuum was gone (it had been the first item I had sealed). I made a fish-pie out of the tuna. As this was the worst part, I didn't expect anything great of it, but it was salted, apart from having a strong flavor. I attribute the strong flavor to the cut (the dark part, mostly) and from having been in the fridge for a week).

One piece of prime cut that I had sealed in with the other meat, I reserved and grilled the next day. It was also salted.

Would this be because I salted it too heavily, or can it be because it had been sitting during one week? Is tuna meat salty on it's own? Any other suggestion?

Answer

As far as I know, raw tuna is not usually salted and/or pre-treated.

What may be happening is a case of perceived salinity. For example, there are numerous studies that suggest foods with certain odors can be perceived as much saltier than they actually are. If you have access to that second article (it is copyrighted and behind a paywall, so I can't post it here), it has a great figure on page 3 depicting the perceived sourness, bitterness, sweetness, and saltiness of a number of common foods, including tuna. The aroma of plain tuna alone ranked higher than soy sauce on the saltiness scale, for example. Tuna is relatively high in fat, and other studies suggest that high fat foods can also increase perceived saltiness. Perhaps you were using a fattier part of the fish?

Finally, there is evidence that dehydration increases the saltiness of tuna (which actually seems somewhat intuitive), especially if extra salt is added before cooking. Was your tuna previously frozen? Freezing—especially if done improperly and/or if there are multiple freeze/thaw cycles—can act like dehydration.

Check more discussion of this question.